Sierpinski carpet fractal microstrip antenna for improved bandwidth using stacking technique with probe feeding

1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
8
SIERPINSKI CARPET FRACTAL MICROSTRIP
ANTENNA FOR IMPROVED BANDWIDTH USING
STACKING TECHNIQUE WITH PROBE FEEDING
Sudhina H. K.1
, Dr. Jagadeesha S.2
, Dr. N. M. Shetti3
, Dr.Girish Attimarad4
1
Associate Professor & Head, E & CE Dept., REC, Hulkoti, Gadag, India,
Ph.D Scholar at St. Peter’s University, Chennai, India
2
Professor, E & CE Dept., S.D.M.I.T, Ujire, Karnataka (D.K), India
3
Professor, Dept. of Physics, S.D.M College, Ujire, Karnataka (D.K.), India
4
Professor, E & CE Dept., Dayanand Sagar College of Engineering, Bangalore
ABSTRACT
This research article outlines Sierpinski carpet fractal microstrip antenna for bandwidth
enhancement using probe feeding technique from reference to third iterations. Prototype antenna
is designed on FR4 substrate with thickness of 1.6 mm whose relative dielectric constant of 4.4.
These antennas are optimized to operate under various specified bands between 2-14 GHz.
Simulation is carried out using IE3D simulator and it is found that the simulated results are in
good agreement with the experimental results. Stacking techniques are also implemented on the
designed antenna using probe feeding for further enhancement of bandwidth. Comparison is
carried out with reference to without and with stacking method.
Keywords: Microstrip Antennas, Sierpinski, Multiband, Iterations, Stacking, Probe Feed
1. INTRODUCTION
Modern wireless communication systems and increase of other wireless applications,
wider bandwidth and low profile antennas are in great demand for both commercial and military
applications [1]. The science of fractal offers us new interesting possibilities for designing small
broadband and efficient antennas for restricted space. So we focus on nature-based antenna design
concepts which employ fractal geometry. Fractals are space filling contours; means having
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
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electrically large features can be efficiently packed into small areas. Since electrical lengths play
an important role in antenna designs, this efficient packing can be used as a viable miniaturization
technique. A similar set is one that consists of scaled down copies of itself i.e. a contraction which
reduces an image by same factors horizontally and vertically [2]. A microstrip antenna is
characterized by its length, width, input impedance, gain and radiation patterns. The length of the
antenna is nearly half the wavelength in the dielectric; it is a very critical parameter, which
governs the resonant frequency of the antenna [3]. Sierpinski carpet fractal antenna is the most
widely studied fractal geometry for antenna applications. The fractal antenna consists of
geometrical shapes that are repeated. Each one has a unique attribute. The self similarity that
distributed on this antenna expected to cause its multi-band characteristic. On the other hand, it
can solve a traditional antenna that operates at single frequency [4]. The fractal geometry can be
combined with electromagnetic theory for the purpose of investigations. One of the most
promising areas of fractal electrodynamics research is its application to antenna theory and design
[5]. Applying fractals to the antenna elements allows for smaller size, multi-band and broad-band
properties [6]. By stacking a parasitic patch on a microstrip patch antenna, the antenna with high
gain or wide bandwidth can be realized [7].
2. ANTENNA DESIGN
2.1 Design Calculation
The sierpinski fractal microstrip antenna is applied with probe feed which isconsidered as
the reference antenna i.e. it is a base antenna as shown in the Fig.1(a). Dimension is 54 mm *54
mm which is printed on a dielectric substrate of thickness 1.6 mm. Material used is FR4 substrate
having a dielectric constant of ℇr = 4.4 which are operated over various bands of frequencies. This
designed antenna is fed by probe of 50 ohm impedance. The construction of the sierpinski carpet
begins with a square. The square is cut into 9 congruent sub squares in a 3-by-3 grid and the
central sub-square is removed. The same procedure is then applied recursively to the remaining 8
sub squares. The area of the carpet is zero (in standard Lebesgue measure). The Hausdorff
dimension of the carpet is log 8 / logs 3 ≈ 1.8928. for both without stacked and. Comparison of
stacked and non stacked sierpinski carpet fractal microstrip antenna is made and summarized as
below:
2.2 Sierpinski carpet mistrostrip fractal antennas with probe feeding without stacking
Fig.1(a) is the reference antenna. Fig. 1(b), 1(c) and 1(d) show 1st
, 2nd
and 3rd
respectively.
The Fig.2 shows iterations of the fabricated view of the designed antennas.
1(a) 1(b) 1(c) 1(d)
Fig.1 Geometry of reference, 1st
, 2nd
and 3rd
iterated antennas

3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
10
Fig.2 Fabricated view of base antenna, 1st
, 2nd
and 3rd
iterated antennas
2.3 Sierpinski carpet mistrostrip fractal antennas with probe feeding and stacking
The stacking technique is implemented on sierpinski carpet fractal microstrip antenna for
the ref, 1st
, 2nd
and 3rd
iterations. Fig.3 shows the fabricated view of the above antennas, for
microstrip probe feed.
Fig.3 Fabricated view of Stacked Sierpinski carpet mistrostrip fractal antennas
3. RESULTS AND DISCUSSIONS
Sierpinski fractal microstrip antennas were examined for without & with stacking using
IE3D simulation tool. The parameters like return loss, bandwidth were analyzed using well
known simulator IE3D and it was verified using vector network analyzer. Simulated results were
found in good agreement with the experimental analysis.
Fig.4, Fig.6, Fig.8 and Fig.10 show the results of simulated return loss characteristics and
Fig.5, Fig.7, Fig.9 and Fig.11 shows the corresponding practical return loss characteristics taken
out from vector Network analyzer. Table1 summarizes the various results of the performance
parameters like the variation of bandwidth, resonant frequency, return loss and gain with
reference to without and with stacking of sierpinski carpet fractal microstrip antenna. The best
wide possible resonant frequency is operating around 6 GHz. Various iterations were statistically
analysed and which are summarized in the table1. Fig 12 & Fig.13 show the graph of gain vs
frequency for without stacked and stacked structure.

4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
11
4(a) (4b)
Fig.4 simulated return loss characteristics of without and with stacking of reference antenna
implemented on sierpinski fractal
(5a) (5b)
Fig.5 practical return loss characteristics of without and with stacking of reference antenna
implemented on sierpinski fractal
6(a) 6(b)
Fig.6 simulated return loss characteristics of without and with stacking of 1st
iteration antenna
implemented on sierpinski fractal

5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
12
7(a) 7(b)
Fig.7 practical return loss characteristics of without and with stacking of 1st
iteration antenna
implemented on sierpinski fractal
8(a) 8(b)
Fig.8 simulated return loss characteristics of without and with stacking of 2nd
iteration antenna
implemented on sierpinski fractal
9(a) (9b)
Fig.9 practical simulated return loss characteristics of without and with stacking of
2nd
iteration antenna implemented on sierpinski fractal

6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
13
10(a) 10(b)
Fig.10 simulated return loss characteristics of without and with stacking of 3rd
iteration antenna
implemented on sierpinski fractal
11(a) 11(b)
Fig.11 practical return loss characteristics of without and with stacking of 3rd
iteration antenna
implemented on sierpinski fractal
12(a) 12(b)

7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
14
12(c) 12(d)
Fig.12 Frequency vs gain for without stack
13(a) 13(b)
13(c) 13(d)
Fig.13 Frequency vs gain for with stack

8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
15
Table: 1 Result of the simulated and experimental values for stacked and without stacked
For without stacking, the reference antenna displays the resonant frequency of -14 db at 6
GHz with a gain of -1db and a bandwidth of 75 MHz and in the experimental analysis value
observed is resonant frequency at -12.9 db with a bandwidth of i.e 80 MHz. With stacking, the
simulated values for the reference antenna displays the resonant frequency of -15db, with a
bandwidth of 150 MHz and experimental analysis shows -13.5db with increase of bandwidth to
120 MHz, after stacking.
After first iteration, the resonant frequency shifts in significant as summarized in Table.1.
Result of different antennas with the various resonant frequencies whose characteristic features
like return loss and band width are summarized. Experimental results are in close agreement with
the simulated results using IE3D software. The resonating frequency seems to be shifted to right
with increase of the iterations for both the cases, without and with stacking.
4. CONCLUSION
This paper presents a design of sierpinski carpet microstrip fractal antenna for probe feed,
without stack and with stacking are carried out for a multiband operation. A comparison is made
with reference to without and with stacking. The optimized bandwidths obtained are 45 MHz and
60 MHz for simulated and practical analysis respectively. An improvement of gain is obtained
from -1db to 3db for without stacking and it is 0.5 db to 5 db for stacking.
REFERENCES
1. Ruchi Singh and Hamid Ali, “Design of Sierpinski Carpet Fractal Antenna”, International
Journal of Emerging Trends in Electrical and Electronics Vol. 7, Issue 2, 18-21, 2013
2. Rohit Gurjar, Smrity Dwidevi Shivakant Thakur and madhur Jain, “A self- affine -8 -
shaped fractal multiband antenna for wireless applications”, International journal of
electronics, vol. 4, Issue 2, 103-108, 2013
Iterations for
probe feeding
Resonant
frequency (GHz)
Return loss(dB) Gain
(dBi)
Bandwidth
(MHz)
Simulat
ed
Experi
ment
Simulat
ed
Experim
ent
Simula
ted
simula
ted
Experi
ment
Reference iteration antenna
Without stack 6.0 6.4 -12 -12.9 -1 75 80
With stack 6.0 6.0 -15 -13.5 0.5 150 120
1st
iteration Antenna
Without stack 6.4 6.5 -22 -12 3 175 200
With stack for 6.4 6.51 -12.87 -20.54 1 250 260
2nd
iteration Antenna
Without stack 6.5 6.62 -13.5 -11.47 2.0 200 275
With stack 6.5 6.6 -11 -13 5.0 210 300
3rd
iteration Antenna
Without stack 6.6 6.5 -16 -16 3.0 255 290
With stack 6.6 6.5 -17. 2 -19.76 5.32 300 350

9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 6, Issue 1, January (2015), pp. 08-16 © IAEME
16
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SSRG International Journal of Electronics and Communication Engineering, vol.1, Issue7,
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The theory and design of fractal Antenna”, 2010
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Researchers Club, Islamic Azad University, Gonabad Branch, Iran Progress In
Electromagnetics Research Symposium Proceedings, Cambridge, USA, 2010
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gain”, Progress In Electromagnetics Research, PIER 33, 29–43, 2001.